Lumbar facet joints serve neurophysiological as well as biomechanical functions and, when subject to noxious stimulation, can produce low back pain. The facet joints are comprised of the articulating processes of adjacent vertebrae and a ligamentous capsule that tends to constrain the articular movements. As loads are transmitted by the facet joints, the joint surfaces move relative to each other and the capsule is deformed. Capsular deformations are thought to be an adequate neurological stimulus, evoking the discharge of sensory nerves innervating the capsule. Since the capsule is innervated by mechanoreceptors and nociceptors, it may function to signal position or loading of the facet joint. However, to date there are few quantitative studies of the mechanical state of the facet capsule during normal physiological ranges of motion of the spine. Thus, it is unknown if the capsule can be sufficiently loaded under physiological conditions to result in stimulation of the mechanically sensitive neurons known to innervate it. The long term goal of the investigators is to understand the functional interactions between spinal biomechanics and the nervous system. Knowledge gained through these studies will provide important and novel information regarding the mechanisms by which spine disorders can affect the nervous system. For example, disc degeneration and chemonucleolysis may increase the load on the facets. Until we know how the facet capsules respond under load, we will not be able to determine the relevance of these changes to the pathogenesis of low back pain. The short range goal of the investigators is to elucidate how the human facet joint capsule is loaded during physiological loads of the lumbar spine and to develop a computational model that will enable us to ultimately examine how manipulations of the spine affect capsule loading. This project, using un-embalmed human cadaveric lumbar spines, will: 1) Measure the plane strains developed during physiological motions of the lumbar spine; 2) Determine material properties of the facet joint capsule; and 3) Develop a mathematical model of the capsule using finite element analysis to enable estimating stress at any location within the capsule during loading.